// SPDX-License-Identifier: GPL-2.0+ OR BSD-3-Clause
/*
 * f_mass_storage.c -- Mass Storage USB Composite Function
 *
 * Copyright (C) 2003-2008 Alan Stern
 * Copyright (C) 2009 Samsung Electronics
 *                    Author: Michal Nazarewicz <m.nazarewicz@samsung.com>
 * All rights reserved.
 */

/*
 * The Mass Storage Function acts as a USB Mass Storage device,
 * appearing to the host as a disk drive or as a CD-ROM drive.  In
 * addition to providing an example of a genuinely useful composite
 * function for a USB device, it also illustrates a technique of
 * double-buffering for increased throughput.
 *
 * Function supports multiple logical units (LUNs).  Backing storage
 * for each LUN is provided by a regular file or a block device.
 * Access for each LUN can be limited to read-only.  Moreover, the
 * function can indicate that LUN is removable and/or CD-ROM.  (The
 * later implies read-only access.)
 *
 * MSF is configured by specifying a fsg_config structure.  It has the
 * following fields:
 *
 *      nluns           Number of LUNs function have (anywhere from 1
 *                              to FSG_MAX_LUNS which is 8).
 *      luns            An array of LUN configuration values.  This
 *                              should be filled for each LUN that
 *                              function will include (ie. for "nluns"
 *                              LUNs).  Each element of the array has
 *                              the following fields:
 *      ->filename      The path to the backing file for the LUN.
 *                              Required if LUN is not marked as
 *                              removable.
 *      ->ro            Flag specifying access to the LUN shall be
 *                              read-only.  This is implied if CD-ROM
 *                              emulation is enabled as well as when
 *                              it was impossible to open "filename"
 *                              in R/W mode.
 *      ->removable     Flag specifying that LUN shall be indicated as
 *                              being removable.
 *      ->cdrom         Flag specifying that LUN shall be reported as
 *                              being a CD-ROM.
 *
 *      lun_name_format A printf-like format for names of the LUN
 *                              devices.  This determines how the
 *                              directory in sysfs will be named.
 *                              Unless you are using several MSFs in
 *                              a single gadget (as opposed to single
 *                              MSF in many configurations) you may
 *                              leave it as NULL (in which case
 *                              "lun%d" will be used).  In the format
 *                              you can use "%d" to index LUNs for
 *                              MSF's with more than one LUN.  (Beware
 *                              that there is only one integer given
 *                              as an argument for the format and
 *                              specifying invalid format may cause
 *                              unspecified behaviour.)
 *      thread_name     Name of the kernel thread process used by the
 *                              MSF.  You can safely set it to NULL
 *                              (in which case default "file-storage"
 *                              will be used).
 *
 *      vendor_name
 *      product_name
 *      release         Information used as a reply to INQUIRY
 *                              request.  To use default set to NULL,
 *                              NULL, 0xffff respectively.  The first
 *                              field should be 8 and the second 16
 *                              characters or less.
 *
 *      can_stall       Set to permit function to halt bulk endpoints.
 *                              Disabled on some USB devices known not
 *                              to work correctly.  You should set it
 *                              to true.
 *
 * If "removable" is not set for a LUN then a backing file must be
 * specified.  If it is set, then NULL filename means the LUN's medium
 * is not loaded (an empty string as "filename" in the fsg_config
 * structure causes error).  The CD-ROM emulation includes a single
 * data track and no audio tracks; hence there need be only one
 * backing file per LUN.  Note also that the CD-ROM block length is
 * set to 512 rather than the more common value 2048.
 *
 *
 * MSF includes support for module parameters.  If gadget using it
 * decides to use it, the following module parameters will be
 * available:
 *
 *      file=filename[,filename...]
 *                      Names of the files or block devices used for
 *                              backing storage.
 *      ro=b[,b...]     Default false, boolean for read-only access.
 *      removable=b[,b...]
 *                      Default true, boolean for removable media.
 *      cdrom=b[,b...]  Default false, boolean for whether to emulate
 *                              a CD-ROM drive.
 *      luns=N          Default N = number of filenames, number of
 *                              LUNs to support.
 *      stall           Default determined according to the type of
 *                              USB device controller (usually true),
 *                              boolean to permit the driver to halt
 *                              bulk endpoints.
 *
 * The module parameters may be prefixed with some string.  You need
 * to consult gadget's documentation or source to verify whether it is
 * using those module parameters and if it does what are the prefixes
 * (look for FSG_MODULE_PARAMETERS() macro usage, what's inside it is
 * the prefix).
 *
 *
 * Requirements are modest; only a bulk-in and a bulk-out endpoint are
 * needed.  The memory requirement amounts to two 16K buffers, size
 * configurable by a parameter.  Support is included for both
 * full-speed and high-speed operation.
 *
 * Note that the driver is slightly non-portable in that it assumes a
 * single memory/DMA buffer will be useable for bulk-in, bulk-out, and
 * interrupt-in endpoints.  With most device controllers this isn't an
 * issue, but there may be some with hardware restrictions that prevent
 * a buffer from being used by more than one endpoint.
 *
 *
 * The pathnames of the backing files and the ro settings are
 * available in the attribute files "file" and "ro" in the lun<n> (or
 * to be more precise in a directory which name comes from
 * "lun_name_format" option!) subdirectory of the gadget's sysfs
 * directory.  If the "removable" option is set, writing to these
 * files will simulate ejecting/loading the medium (writing an empty
 * line means eject) and adjusting a write-enable tab.  Changes to the
 * ro setting are not allowed when the medium is loaded or if CD-ROM
 * emulation is being used.
 *
 * When a LUN receive an "eject" SCSI request (Start/Stop Unit),
 * if the LUN is removable, the backing file is released to simulate
 * ejection.
 *
 *
 * This function is heavily based on "File-backed Storage Gadget" by
 * Alan Stern which in turn is heavily based on "Gadget Zero" by David
 * Brownell.  The driver's SCSI command interface was based on the
 * "Information technology - Small Computer System Interface - 2"
 * document from X3T9.2 Project 375D, Revision 10L, 7-SEP-93,
 * available at <http://www.t10.org/ftp/t10/drafts/s2/s2-r10l.pdf>.
 * The single exception is opcode 0x23 (READ FORMAT CAPACITIES), which
 * was based on the "Universal Serial Bus Mass Storage Class UFI
 * Command Specification" document, Revision 1.0, December 14, 1998,
 * available at
 * <http://www.usb.org/developers/devclass_docs/usbmass-ufi10.pdf>.
 */

/*
 *                              Driver Design
 *
 * The MSF is fairly straightforward.  There is a main kernel
 * thread that handles most of the work.  Interrupt routines field
 * callbacks from the controller driver: bulk- and interrupt-request
 * completion notifications, endpoint-0 events, and disconnect events.
 * Completion events are passed to the main thread by wakeup calls.  Many
 * ep0 requests are handled at interrupt time, but SetInterface,
 * SetConfiguration, and device reset requests are forwarded to the
 * thread in the form of "exceptions" using SIGUSR1 signals (since they
 * should interrupt any ongoing file I/O operations).
 *
 * The thread's main routine implements the standard command/data/status
 * parts of a SCSI interaction.  It and its subroutines are full of tests
 * for pending signals/exceptions -- all this polling is necessary since
 * the kernel has no setjmp/longjmp equivalents.  (Maybe this is an
 * indication that the driver really wants to be running in userspace.)
 * An important point is that so long as the thread is alive it keeps an
 * open reference to the backing file.  This will prevent unmounting
 * the backing file's underlying filesystem and could cause problems
 * during system shutdown, for example.  To prevent such problems, the
 * thread catches INT, TERM, and KILL signals and converts them into
 * an EXIT exception.
 *
 * In normal operation the main thread is started during the gadget's
 * fsg_bind() callback and stopped during fsg_unbind().  But it can
 * also exit when it receives a signal, and there's no point leaving
 * the gadget running when the thread is dead.  At of this moment, MSF
 * provides no way to deregister the gadget when thread dies -- maybe
 * a callback functions is needed.
 *
 * To provide maximum throughput, the driver uses a circular pipeline of
 * buffer heads (struct fsg_buffhd).  In principle the pipeline can be
 * arbitrarily long; in practice the benefits don't justify having more
 * than 2 stages (i.e., double buffering).  But it helps to think of the
 * pipeline as being a long one.  Each buffer head contains a bulk-in and
 * a bulk-out request pointer (since the buffer can be used for both
 * output and input -- directions always are given from the host's
 * point of view) as well as a pointer to the buffer and various state
 * variables.
 *
 * Use of the pipeline follows a simple protocol.  There is a variable
 * (fsg->next_buffhd_to_fill) that points to the next buffer head to use.
 * At any time that buffer head may still be in use from an earlier
 * request, so each buffer head has a state variable indicating whether
 * it is EMPTY, FULL, or BUSY.  Typical use involves waiting for the
 * buffer head to be EMPTY, filling the buffer either by file I/O or by
 * USB I/O (during which the buffer head is BUSY), and marking the buffer
 * head FULL when the I/O is complete.  Then the buffer will be emptied
 * (again possibly by USB I/O, during which it is marked BUSY) and
 * finally marked EMPTY again (possibly by a completion routine).
 *
 * A module parameter tells the driver to avoid stalling the bulk
 * endpoints wherever the transport specification allows.  This is
 * necessary for some UDCs like the SuperH, which cannot reliably clear a
 * halt on a bulk endpoint.  However, under certain circumstances the
 * Bulk-only specification requires a stall.  In such cases the driver
 * will halt the endpoint and set a flag indicating that it should clear
 * the halt in software during the next device reset.  Hopefully this
 * will permit everything to work correctly.  Furthermore, although the
 * specification allows the bulk-out endpoint to halt when the host sends
 * too much data, implementing this would cause an unavoidable race.
 * The driver will always use the "no-stall" approach for OUT transfers.
 *
 * One subtle point concerns sending status-stage responses for ep0
 * requests.  Some of these requests, such as device reset, can involve
 * interrupting an ongoing file I/O operation, which might take an
 * arbitrarily long time.  During that delay the host might give up on
 * the original ep0 request and issue a new one.  When that happens the
 * driver should not notify the host about completion of the original
 * request, as the host will no longer be waiting for it.  So the driver
 * assigns to each ep0 request a unique tag, and it keeps track of the
 * tag value of the request associated with a long-running exception
 * (device-reset, interface-change, or configuration-change).  When the
 * exception handler is finished, the status-stage response is submitted
 * only if the current ep0 request tag is equal to the exception request
 * tag.  Thus only the most recently received ep0 request will get a
 * status-stage response.
 *
 * Warning: This driver source file is too long.  It ought to be split up
 * into a header file plus about 3 separate .c files, to handle the details
 * of the Gadget, USB Mass Storage, and SCSI protocols.
 */

/* #define VERBOSE_DEBUG */
/* #define DUMP_MSGS */

#include <config.h>
#include <hexdump.h>
#include <log.h>
#include <malloc.h>
#include <common.h>
#include <console.h>
#include <g_dnl.h>
#include <dm/devres.h>
#include <linux/bug.h>

#include <linux/err.h>
#include <linux/usb/ch9.h>
#include <linux/usb/gadget.h>
#include <usb_mass_storage.h>

#include <asm/unaligned.h>
#include <linux/bitops.h>
#include <linux/usb/gadget.h>
#include <linux/usb/gadget.h>
#include <linux/usb/composite.h>
#include <linux/bitmap.h>
#include <g_dnl.h>

/*------------------------------------------------------------------------*/

#define FSG_DRIVER_DESC "Mass Storage Function"
#define FSG_DRIVER_VERSION      "2012/06/5"

static const char fsg_string_interface[] = "Mass Storage";

#define FSG_NO_INTR_EP 1
#define FSG_NO_DEVICE_STRINGS    1
#define FSG_NO_OTG               1
#define FSG_NO_INTR_EP           1

#include "storage_common.c"

/*-------------------------------------------------------------------------*/

#define GFP_ATOMIC ((gfp_t) 0)
#define PAGE_CACHE_SHIFT        12
#define PAGE_CACHE_SIZE         (1 << PAGE_CACHE_SHIFT)
#define kthread_create(...)     __builtin_return_address(0)
#define wait_for_completion(...) do {} while (0)

struct kref {int x; };
struct completion {int x; };

struct fsg_dev;
struct fsg_common;

/* Data shared by all the FSG instances. */
struct fsg_common {
        struct usb_gadget       *gadget;
        struct fsg_dev          *fsg, *new_fsg;

        struct usb_ep           *ep0;           /* Copy of gadget->ep0 */
        struct usb_request      *ep0req;        /* Copy of cdev->req */
        unsigned int            ep0_req_tag;

        struct fsg_buffhd       *next_buffhd_to_fill;
        struct fsg_buffhd       *next_buffhd_to_drain;
        struct fsg_buffhd       buffhds[FSG_NUM_BUFFERS];

        int                     cmnd_size;
        u8                      cmnd[MAX_COMMAND_SIZE];

        unsigned int            nluns;
        unsigned int            lun;
        struct fsg_lun          luns[FSG_MAX_LUNS];

        unsigned int            bulk_out_maxpacket;
        enum fsg_state          state;          /* For exception handling */
        unsigned int            exception_req_tag;

        enum data_direction     data_dir;
        u32                     data_size;
        u32                     data_size_from_cmnd;
        u32                     tag;
        u32                     residue;
        u32                     usb_amount_left;

        unsigned int            can_stall:1;
        unsigned int            free_storage_on_release:1;
        unsigned int            phase_error:1;
        unsigned int            short_packet_received:1;
        unsigned int            bad_lun_okay:1;
        unsigned int            running:1;

        int                     thread_wakeup_needed;
        struct completion       thread_notifier;
        struct task_struct      *thread_task;

        /* Callback functions. */
        const struct fsg_operations     *ops;
        /* Gadget's private data. */
        void                    *private_data;

        const char *vendor_name;                /*  8 characters or less */
        const char *product_name;               /* 16 characters or less */
        u16 release;

        /* Vendor (8 chars), product (16 chars), release (4
         * hexadecimal digits) and NUL byte */
        char inquiry_string[8 + 16 + 4 + 1];

        struct kref             ref;
};

struct fsg_config {
        unsigned nluns;
        struct fsg_lun_config {
                const char *filename;
                char ro;
                char removable;
                char cdrom;
                char nofua;
        } luns[FSG_MAX_LUNS];

        /* Callback functions. */
        const struct fsg_operations     *ops;
        /* Gadget's private data. */
        void                    *private_data;

        const char *vendor_name;                /*  8 characters or less */
        const char *product_name;               /* 16 characters or less */

        char                    can_stall;
};

struct fsg_dev {
        struct usb_function     function;
        struct usb_gadget       *gadget;        /* Copy of cdev->gadget */
        struct fsg_common       *common;

        u16                     interface_number;

        unsigned int            bulk_in_enabled:1;
        unsigned int            bulk_out_enabled:1;

        unsigned long           atomic_bitflags;
#define IGNORE_BULK_OUT         0

        struct usb_ep           *bulk_in;
        struct usb_ep           *bulk_out;
};


static inline int __fsg_is_set(struct fsg_common *common,
                               const char *func, unsigned line)
{
        if (common->fsg)
                return 1;
        ERROR(common, "common->fsg is NULL in %s at %u\n", func, line);
#ifdef __UBOOT__
        assert_noisy(false);
#else
        WARN_ON(1);
#endif
        return 0;
}

#define fsg_is_set(common) likely(__fsg_is_set(common, __func__, __LINE__))


static inline struct fsg_dev *fsg_from_func(struct usb_function *f)
{
        return container_of(f, struct fsg_dev, function);
}


typedef void (*fsg_routine_t)(struct fsg_dev *);

static int exception_in_progress(struct fsg_common *common)
{
        return common->state > FSG_STATE_IDLE;
}

/* Make bulk-out requests be divisible by the maxpacket size */
static void set_bulk_out_req_length(struct fsg_common *common,
                struct fsg_buffhd *bh, unsigned int length)
{
        unsigned int    rem;

        bh->bulk_out_intended_length = length;
        rem = length % common->bulk_out_maxpacket;
        if (rem > 0)
                length += common->bulk_out_maxpacket - rem;
        bh->outreq->length = length;
}

/*-------------------------------------------------------------------------*/

static struct ums *ums;
static int ums_count;
static struct fsg_common *the_fsg_common;
static unsigned int controller_index;

static int fsg_set_halt(struct fsg_dev *fsg, struct usb_ep *ep)
{
        const char      *name;

        if (ep == fsg->bulk_in)
                name = "bulk-in";
        else if (ep == fsg->bulk_out)
                name = "bulk-out";
        else
                name = ep->name;
        DBG(fsg, "%s set halt\n", name);
        return usb_ep_set_halt(ep);
}

/*-------------------------------------------------------------------------*/

/* These routines may be called in process context or in_irq */

/* Caller must hold fsg->lock */
static void wakeup_thread(struct fsg_common *common)
{
        common->thread_wakeup_needed = 1;
}

static void raise_exception(struct fsg_common *common, enum fsg_state new_state)
{
        /* Do nothing if a higher-priority exception is already in progress.
         * If a lower-or-equal priority exception is in progress, preempt it
         * and notify the main thread by sending it a signal. */
        if (common->state <= new_state) {
                common->exception_req_tag = common->ep0_req_tag;
                common->state = new_state;
                common->thread_wakeup_needed = 1;
        }
}

/*-------------------------------------------------------------------------*/

static int ep0_queue(struct fsg_common *common)
{
        int     rc;

        rc = usb_ep_queue(common->ep0, common->ep0req, GFP_ATOMIC);
        common->ep0->driver_data = common;
        if (rc != 0 && rc != -ESHUTDOWN) {
                /* We can't do much more than wait for a reset */
                WARNING(common, "error in submission: %s --> %d\n",
                        common->ep0->name, rc);
        }
        return rc;
}

/*-------------------------------------------------------------------------*/

/* Bulk and interrupt endpoint completion handlers.
 * These always run in_irq. */

static void bulk_in_complete(struct usb_ep *ep, struct usb_request *req)
{
        struct fsg_common       *common = ep->driver_data;
        struct fsg_buffhd       *bh = req->context;

        if (req->status || req->actual != req->length)
                DBG(common, "%s --> %d, %u/%u\n", __func__,
                                req->status, req->actual, req->length);
        if (req->status == -ECONNRESET)         /* Request was cancelled */
                usb_ep_fifo_flush(ep);

        /* Hold the lock while we update the request and buffer states */
        bh->inreq_busy = 0;
        bh->state = BUF_STATE_EMPTY;
        wakeup_thread(common);
}

static void bulk_out_complete(struct usb_ep *ep, struct usb_request *req)
{
        struct fsg_common       *common = ep->driver_data;
        struct fsg_buffhd       *bh = req->context;

        dump_msg(common, "bulk-out", req->buf, req->actual);
        if (req->status || req->actual != bh->bulk_out_intended_length)
                DBG(common, "%s --> %d, %u/%u\n", __func__,
                                req->status, req->actual,
                                bh->bulk_out_intended_length);
        if (req->status == -ECONNRESET)         /* Request was cancelled */
                usb_ep_fifo_flush(ep);

        /* Hold the lock while we update the request and buffer states */
        bh->outreq_busy = 0;
        bh->state = BUF_STATE_FULL;
        wakeup_thread(common);
}

/*-------------------------------------------------------------------------*/

/* Ep0 class-specific handlers.  These always run in_irq. */

static int fsg_setup(struct usb_function *f,
                const struct usb_ctrlrequest *ctrl)
{
        struct fsg_dev          *fsg = fsg_from_func(f);
        struct usb_request      *req = fsg->common->ep0req;
        u16                     w_index = get_unaligned_le16(&ctrl->wIndex);
        u16                     w_value = get_unaligned_le16(&ctrl->wValue);
        u16                     w_length = get_unaligned_le16(&ctrl->wLength);

        if (!fsg_is_set(fsg->common))
                return -EOPNOTSUPP;

        switch (ctrl->bRequest) {

        case USB_BULK_RESET_REQUEST:
                if (ctrl->bRequestType !=
                    (USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE))
                        break;
                if (w_index != fsg->interface_number || w_value != 0)
                        return -EDOM;

                /* Raise an exception to stop the current operation
                 * and reinitialize our state. */
                DBG(fsg, "bulk reset request\n");
                raise_exception(fsg->common, FSG_STATE_RESET);
                return DELAYED_STATUS;

        case USB_BULK_GET_MAX_LUN_REQUEST:
                if (ctrl->bRequestType !=
                    (USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE))
                        break;
                if (w_index != fsg->interface_number || w_value != 0)
                        return -EDOM;
                VDBG(fsg, "get max LUN\n");
                *(u8 *) req->buf = fsg->common->nluns - 1;

                /* Respond with data/status */
                req->length = min((u16)1, w_length);
                return ep0_queue(fsg->common);
        }

        VDBG(fsg,
             "unknown class-specific control req "
             "%02x.%02x v%04x i%04x l%u\n",
             ctrl->bRequestType, ctrl->bRequest,
             get_unaligned_le16(&ctrl->wValue), w_index, w_length);
        return -EOPNOTSUPP;
}

/*-------------------------------------------------------------------------*/

/* All the following routines run in process context */

/* Use this for bulk or interrupt transfers, not ep0 */
static void start_transfer(struct fsg_dev *fsg, struct usb_ep *ep,
                struct usb_request *req, int *pbusy,
                enum fsg_buffer_state *state)
{
        int     rc;

        if (ep == fsg->bulk_in)
                dump_msg(fsg, "bulk-in", req->buf, req->length);

        *pbusy = 1;
        *state = BUF_STATE_BUSY;
        rc = usb_ep_queue(ep, req, GFP_KERNEL);
        if (rc != 0) {
                *pbusy = 0;
                *state = BUF_STATE_EMPTY;

                /* We can't do much more than wait for a reset */

                /* Note: currently the net2280 driver fails zero-length
                 * submissions if DMA is enabled. */
                if (rc != -ESHUTDOWN && !(rc == -EOPNOTSUPP &&
                                                req->length == 0))
                        WARNING(fsg, "error in submission: %s --> %d\n",
                                        ep->name, rc);
        }
}

#define START_TRANSFER_OR(common, ep_name, req, pbusy, state)           \
        if (fsg_is_set(common))                                         \
                start_transfer((common)->fsg, (common)->fsg->ep_name,   \
                               req, pbusy, state);                      \
        else

#define START_TRANSFER(common, ep_name, req, pbusy, state)              \
        START_TRANSFER_OR(common, ep_name, req, pbusy, state) (void)0

static void busy_indicator(void)
{
        static int state;

        switch (state) {
        case 0:
                puts("\r|"); break;
        case 1:
                puts("\r/"); break;
        case 2:
                puts("\r-"); break;
        case 3:
                puts("\r\\"); break;
        case 4:
                puts("\r|"); break;
        case 5:
                puts("\r/"); break;
        case 6:
                puts("\r-"); break;
        case 7:
                puts("\r\\"); break;
        default:
                state = 0;
        }
        if (state++ == 8)
                state = 0;
}

static int sleep_thread(struct fsg_common *common)
{
        int     rc = 0;
        int i = 0, k = 0;

        /* Wait until a signal arrives or we are woken up */
        for (;;) {
                if (common->thread_wakeup_needed)
                        break;

                if (++i == 20000) {
                        busy_indicator();
                        i = 0;
                        k++;
                }

                if (k == 10) {
                        /* Handle CTRL+C */
                        if (ctrlc())
                                return -EPIPE;

                        /* Check cable connection */
                        if (!g_dnl_board_usb_cable_connected())
                                return -EIO;

                        k = 0;
                }

                usb_gadget_handle_interrupts(controller_index);
        }
        common->thread_wakeup_needed = 0;
        return rc;
}

/*-------------------------------------------------------------------------*/

static int do_read(struct fsg_common *common)
{
        struct fsg_lun          *curlun = &common->luns[common->lun];
        u32                     lba;
        struct fsg_buffhd       *bh;
        int                     rc;
        u32                     amount_left;
        loff_t                  file_offset;
        unsigned int            amount;
        unsigned int            partial_page;
        ssize_t                 nread;

        /* Get the starting Logical Block Address and check that it's
         * not too big */
        if (common->cmnd[0] == SC_READ_6)
                lba = get_unaligned_be24(&common->cmnd[1]);
        else {
                lba = get_unaligned_be32(&common->cmnd[2]);

                /* We allow DPO (Disable Page Out = don't save data in the
                 * cache) and FUA (Force Unit Access = don't read from the
                 * cache), but we don't implement them. */
                if ((common->cmnd[1] & ~0x18) != 0) {
                        curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                        return -EINVAL;
                }
        }
        if (lba >= curlun->num_sectors) {
                curlun->sense_data = SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
                return -EINVAL;
        }
        file_offset = ((loff_t) lba) << 9;

        /* Carry out the file reads */
        amount_left = common->data_size_from_cmnd;
        if (unlikely(amount_left == 0))
                return -EIO;            /* No default reply */

        for (;;) {

                /* Figure out how much we need to read:
                 * Try to read the remaining amount.
                 * But don't read more than the buffer size.
                 * And don't try to read past the end of the file.
                 * Finally, if we're not at a page boundary, don't read past
                 *      the next page.
                 * If this means reading 0 then we were asked to read past
                 *      the end of file. */
                amount = min(amount_left, FSG_BUFLEN);
                partial_page = file_offset & (PAGE_CACHE_SIZE - 1);
                if (partial_page > 0)
                        amount = min(amount, (unsigned int) PAGE_CACHE_SIZE -
                                        partial_page);

                /* Wait for the next buffer to become available */
                bh = common->next_buffhd_to_fill;
                while (bh->state != BUF_STATE_EMPTY) {
                        rc = sleep_thread(common);
                        if (rc)
                                return rc;
                }

                /* If we were asked to read past the end of file,
                 * end with an empty buffer. */
                if (amount == 0) {
                        curlun->sense_data =
                                        SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
                        curlun->info_valid = 1;
                        bh->inreq->length = 0;
                        bh->state = BUF_STATE_FULL;
                        break;
                }

                /* Perform the read */
                rc = ums[common->lun].read_sector(&ums[common->lun],
                                      file_offset / SECTOR_SIZE,
                                      amount / SECTOR_SIZE,
                                      (char __user *)bh->buf);
                if (!rc)
                        return -EIO;

                nread = rc * SECTOR_SIZE;

                VLDBG(curlun, "file read %u @ %llu -> %d\n", amount,
                                (unsigned long long) file_offset,
                                (int) nread);

                if (nread < 0) {
                        LDBG(curlun, "error in file read: %d\n",
                                        (int) nread);
                        nread = 0;
                } else if (nread < amount) {
                        LDBG(curlun, "partial file read: %d/%u\n",
                                        (int) nread, amount);
                        nread -= (nread & 511); /* Round down to a block */
                }
                file_offset  += nread;
                amount_left  -= nread;
                common->residue -= nread;
                bh->inreq->length = nread;
                bh->state = BUF_STATE_FULL;

                /* If an error occurred, report it and its position */
                if (nread < amount) {
                        curlun->sense_data = SS_UNRECOVERED_READ_ERROR;
                        curlun->info_valid = 1;
                        break;
                }

                if (amount_left == 0)
                        break;          /* No more left to read */

                /* Send this buffer and go read some more */
                bh->inreq->zero = 0;
                START_TRANSFER_OR(common, bulk_in, bh->inreq,
                               &bh->inreq_busy, &bh->state)
                        /* Don't know what to do if
                         * common->fsg is NULL */
                        return -EIO;
                common->next_buffhd_to_fill = bh->next;
        }

        return -EIO;            /* No default reply */
}

/*-------------------------------------------------------------------------*/

static int do_write(struct fsg_common *common)
{
        struct fsg_lun          *curlun = &common->luns[common->lun];
        u32                     lba;
        struct fsg_buffhd       *bh;
        int                     get_some_more;
        u32                     amount_left_to_req, amount_left_to_write;
        loff_t                  usb_offset, file_offset;
        unsigned int            amount;
        unsigned int            partial_page;
        ssize_t                 nwritten;
        int                     rc;

        if (curlun->ro) {
                curlun->sense_data = SS_WRITE_PROTECTED;
                return -EINVAL;
        }

        /* Get the starting Logical Block Address and check that it's
         * not too big */
        if (common->cmnd[0] == SC_WRITE_6)
                lba = get_unaligned_be24(&common->cmnd[1]);
        else {
                lba = get_unaligned_be32(&common->cmnd[2]);

                /* We allow DPO (Disable Page Out = don't save data in the
                 * cache) and FUA (Force Unit Access = write directly to the
                 * medium).  We don't implement DPO; we implement FUA by
                 * performing synchronous output. */
                if (common->cmnd[1] & ~0x18) {
                        curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                        return -EINVAL;
                }
        }
        if (lba >= curlun->num_sectors) {
                curlun->sense_data = SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
                return -EINVAL;
        }

        /* Carry out the file writes */
        get_some_more = 1;
        file_offset = usb_offset = ((loff_t) lba) << 9;
        amount_left_to_req = common->data_size_from_cmnd;
        amount_left_to_write = common->data_size_from_cmnd;

        while (amount_left_to_write > 0) {

                /* Queue a request for more data from the host */
                bh = common->next_buffhd_to_fill;
                if (bh->state == BUF_STATE_EMPTY && get_some_more) {

                        /* Figure out how much we want to get:
                         * Try to get the remaining amount.
                         * But don't get more than the buffer size.
                         * And don't try to go past the end of the file.
                         * If we're not at a page boundary,
                         *      don't go past the next page.
                         * If this means getting 0, then we were asked
                         *      to write past the end of file.
                         * Finally, round down to a block boundary. */
                        amount = min(amount_left_to_req, FSG_BUFLEN);
                        partial_page = usb_offset & (PAGE_CACHE_SIZE - 1);
                        if (partial_page > 0)
                                amount = min(amount,
        (unsigned int) PAGE_CACHE_SIZE - partial_page);

                        if (amount == 0) {
                                get_some_more = 0;
                                curlun->sense_data =
                                        SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
                                curlun->info_valid = 1;
                                continue;
                        }
                        amount -= (amount & 511);
                        if (amount == 0) {

                                /* Why were we were asked to transfer a
                                 * partial block? */
                                get_some_more = 0;
                                continue;
                        }

                        /* Get the next buffer */
                        usb_offset += amount;
                        common->usb_amount_left -= amount;
                        amount_left_to_req -= amount;
                        if (amount_left_to_req == 0)
                                get_some_more = 0;

                        /* amount is always divisible by 512, hence by
                         * the bulk-out maxpacket size */
                        bh->outreq->length = amount;
                        bh->bulk_out_intended_length = amount;
                        bh->outreq->short_not_ok = 1;
                        START_TRANSFER_OR(common, bulk_out, bh->outreq,
                                          &bh->outreq_busy, &bh->state)
                                /* Don't know what to do if
                                 * common->fsg is NULL */
                                return -EIO;
                        common->next_buffhd_to_fill = bh->next;
                        continue;
                }

                /* Write the received data to the backing file */
                bh = common->next_buffhd_to_drain;
                if (bh->state == BUF_STATE_EMPTY && !get_some_more)
                        break;                  /* We stopped early */
                if (bh->state == BUF_STATE_FULL) {
                        common->next_buffhd_to_drain = bh->next;
                        bh->state = BUF_STATE_EMPTY;

                        /* Did something go wrong with the transfer? */
                        if (bh->outreq->status != 0) {
                                curlun->sense_data = SS_COMMUNICATION_FAILURE;
                                curlun->info_valid = 1;
                                break;
                        }

                        amount = bh->outreq->actual;

                        /* Perform the write */
                        rc = ums[common->lun].write_sector(&ums[common->lun],
                                               file_offset / SECTOR_SIZE,
                                               amount / SECTOR_SIZE,
                                               (char __user *)bh->buf);
                        if (!rc)
                                return -EIO;
                        nwritten = rc * SECTOR_SIZE;

                        VLDBG(curlun, "file write %u @ %llu -> %d\n", amount,
                                        (unsigned long long) file_offset,
                                        (int) nwritten);

                        if (nwritten < 0) {
                                LDBG(curlun, "error in file write: %d\n",
                                                (int) nwritten);
                                nwritten = 0;
                        } else if (nwritten < amount) {
                                LDBG(curlun, "partial file write: %d/%u\n",
                                                (int) nwritten, amount);
                                nwritten -= (nwritten & 511);
                                /* Round down to a block */
                        }
                        file_offset += nwritten;
                        amount_left_to_write -= nwritten;
                        common->residue -= nwritten;

                        /* If an error occurred, report it and its position */
                        if (nwritten < amount) {
                                printf("nwritten:%zd amount:%u\n", nwritten,
                                       amount);
                                curlun->sense_data = SS_WRITE_ERROR;
                                curlun->info_valid = 1;
                                break;
                        }

                        /* Did the host decide to stop early? */
                        if (bh->outreq->actual != bh->outreq->length) {
                                common->short_packet_received = 1;
                                break;
                        }
                        continue;
                }

                /* Wait for something to happen */
                rc = sleep_thread(common);
                if (rc)
                        return rc;
        }

        return -EIO;            /* No default reply */
}

/*-------------------------------------------------------------------------*/

static int do_synchronize_cache(struct fsg_common *common)
{
        return 0;
}

/*-------------------------------------------------------------------------*/

static int do_verify(struct fsg_common *common)

{
        struct fsg_lun          *curlun = &common->luns[common->lun];
        u32                     lba;
        u32                     verification_length;
        struct fsg_buffhd       *bh = common->next_buffhd_to_fill;
        loff_t                  file_offset;
        u32                     amount_left;
        unsigned int            amount;
        ssize_t                 nread;
        int                     rc;

        /* Get the starting Logical Block Address and check that it's
         * not too big */
        lba = get_unaligned_be32(&common->cmnd[2]);
        if (lba >= curlun->num_sectors) {
                curlun->sense_data = SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
                return -EINVAL;
        }

        /* We allow DPO (Disable Page Out = don't save data in the
         * cache) but we don't implement it. */
        if (common->cmnd[1] & ~0x10) {
                curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                return -EINVAL;
        }

        verification_length = get_unaligned_be16(&common->cmnd[7]);
        if (unlikely(verification_length == 0))
                return -EIO;            /* No default reply */

        /* Prepare to carry out the file verify */
        amount_left = verification_length << 9;
        file_offset = ((loff_t) lba) << 9;

        /* Write out all the dirty buffers before invalidating them */

        /* Just try to read the requested blocks */
        while (amount_left > 0) {

                /* Figure out how much we need to read:
                 * Try to read the remaining amount, but not more than
                 * the buffer size.
                 * And don't try to read past the end of the file.
                 * If this means reading 0 then we were asked to read
                 * past the end of file. */
                amount = min(amount_left, FSG_BUFLEN);
                if (amount == 0) {
                        curlun->sense_data =
                                        SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
                        curlun->info_valid = 1;
                        break;
                }

                /* Perform the read */
                rc = ums[common->lun].read_sector(&ums[common->lun],
                                      file_offset / SECTOR_SIZE,
                                      amount / SECTOR_SIZE,
                                      (char __user *)bh->buf);
                if (!rc)
                        return -EIO;
                nread = rc * SECTOR_SIZE;

                VLDBG(curlun, "file read %u @ %llu -> %d\n", amount,
                                (unsigned long long) file_offset,
                                (int) nread);
                if (nread < 0) {
                        LDBG(curlun, "error in file verify: %d\n",
                                        (int) nread);
                        nread = 0;
                } else if (nread < amount) {
                        LDBG(curlun, "partial file verify: %d/%u\n",
                                        (int) nread, amount);
                        nread -= (nread & 511); /* Round down to a sector */
                }
                if (nread == 0) {
                        curlun->sense_data = SS_UNRECOVERED_READ_ERROR;
                        curlun->info_valid = 1;
                        break;
                }
                file_offset += nread;
                amount_left -= nread;
        }
        return 0;
}

/*-------------------------------------------------------------------------*/

static int do_inquiry(struct fsg_common *common, struct fsg_buffhd *bh)
{
        struct fsg_lun *curlun = &common->luns[common->lun];
        static const char vendor_id[] = "Linux   ";
        u8      *buf = (u8 *) bh->buf;

        if (!curlun) {          /* Unsupported LUNs are okay */
                common->bad_lun_okay = 1;
                memset(buf, 0, 36);
                buf[0] = 0x7f;          /* Unsupported, no device-type */
                buf[4] = 31;            /* Additional length */
                return 36;
        }

        memset(buf, 0, 8);
        buf[0] = TYPE_DISK;
        buf[1] = curlun->removable ? 0x80 : 0;
        buf[2] = 2;             /* ANSI SCSI level 2 */
        buf[3] = 2;             /* SCSI-2 INQUIRY data format */
        buf[4] = 31;            /* Additional length */
                                /* No special options */
        sprintf((char *) (buf + 8), "%-8s%-16s%04x", (char*) vendor_id ,
                        ums[common->lun].name, (u16) 0xffff);

        return 36;
}


static int do_request_sense(struct fsg_common *common, struct fsg_buffhd *bh)
{
        struct fsg_lun  *curlun = &common->luns[common->lun];
        u8              *buf = (u8 *) bh->buf;
        u32             sd, sdinfo = 0;
        int             valid;

        /*
         * From the SCSI-2 spec., section 7.9 (Unit attention condition):
         *
         * If a REQUEST SENSE command is received from an initiator
         * with a pending unit attention condition (before the target
         * generates the contingent allegiance condition), then the
         * target shall either:
         *   a) report any pending sense data and preserve the unit
         *      attention condition on the logical unit, or,
         *   b) report the unit attention condition, may discard any
         *      pending sense data, and clear the unit attention
         *      condition on the logical unit for that initiator.
         *
         * FSG normally uses option a); enable this code to use option b).
         */
#if 0
        if (curlun && curlun->unit_attention_data != SS_NO_SENSE) {
                curlun->sense_data = curlun->unit_attention_data;
                curlun->unit_attention_data = SS_NO_SENSE;
        }
#endif

        if (!curlun) {          /* Unsupported LUNs are okay */
                common->bad_lun_okay = 1;
                sd = SS_LOGICAL_UNIT_NOT_SUPPORTED;
                valid = 0;
        } else {
                sd = curlun->sense_data;
                valid = curlun->info_valid << 7;
                curlun->sense_data = SS_NO_SENSE;
                curlun->info_valid = 0;
        }

        memset(buf, 0, 18);
        buf[0] = valid | 0x70;                  /* Valid, current error */
        buf[2] = SK(sd);
        put_unaligned_be32(sdinfo, &buf[3]);    /* Sense information */
        buf[7] = 18 - 8;                        /* Additional sense length */
        buf[12] = ASC(sd);
        buf[13] = ASCQ(sd);
        return 18;
}

static int do_read_capacity(struct fsg_common *common, struct fsg_buffhd *bh)
{
        struct fsg_lun  *curlun = &common->luns[common->lun];
        u32             lba = get_unaligned_be32(&common->cmnd[2]);
        int             pmi = common->cmnd[8];
        u8              *buf = (u8 *) bh->buf;

        /* Check the PMI and LBA fields */
        if (pmi > 1 || (pmi == 0 && lba != 0)) {
                curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                return -EINVAL;
        }

        put_unaligned_be32(curlun->num_sectors - 1, &buf[0]);
                                                /* Max logical block */
        put_unaligned_be32(512, &buf[4]);       /* Block length */
        return 8;
}

static int do_read_header(struct fsg_common *common, struct fsg_buffhd *bh)
{
        struct fsg_lun  *curlun = &common->luns[common->lun];
        int             msf = common->cmnd[1] & 0x02;
        u32             lba = get_unaligned_be32(&common->cmnd[2]);
        u8              *buf = (u8 *) bh->buf;

        if (common->cmnd[1] & ~0x02) {          /* Mask away MSF */
                curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                return -EINVAL;
        }
        if (lba >= curlun->num_sectors) {
                curlun->sense_data = SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
                return -EINVAL;
        }

        memset(buf, 0, 8);
        buf[0] = 0x01;          /* 2048 bytes of user data, rest is EC */
        store_cdrom_address(&buf[4], msf, lba);
        return 8;
}


static int do_read_toc(struct fsg_common *common, struct fsg_buffhd *bh)
{
        struct fsg_lun  *curlun = &common->luns[common->lun];
        int             msf = common->cmnd[1] & 0x02;
        int             start_track = common->cmnd[6];
        u8              *buf = (u8 *) bh->buf;

        if ((common->cmnd[1] & ~0x02) != 0 ||   /* Mask away MSF */
                        start_track > 1) {
                curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                return -EINVAL;
        }

        memset(buf, 0, 20);
        buf[1] = (20-2);                /* TOC data length */
        buf[2] = 1;                     /* First track number */
        buf[3] = 1;                     /* Last track number */
        buf[5] = 0x16;                  /* Data track, copying allowed */
        buf[6] = 0x01;                  /* Only track is number 1 */
        store_cdrom_address(&buf[8], msf, 0);

        buf[13] = 0x16;                 /* Lead-out track is data */
        buf[14] = 0xAA;                 /* Lead-out track number */
        store_cdrom_address(&buf[16], msf, curlun->num_sectors);

        return 20;
}

static int do_mode_sense(struct fsg_common *common, struct fsg_buffhd *bh)
{
        struct fsg_lun  *curlun = &common->luns[common->lun];
        int             mscmnd = common->cmnd[0];
        u8              *buf = (u8 *) bh->buf;
        u8              *buf0 = buf;
        int             pc, page_code;
        int             changeable_values, all_pages;
        int             valid_page = 0;
        int             len, limit;

        if ((common->cmnd[1] & ~0x08) != 0) {   /* Mask away DBD */
                curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                return -EINVAL;
        }
        pc = common->cmnd[2] >> 6;
        page_code = common->cmnd[2] & 0x3f;
        if (pc == 3) {
                curlun->sense_data = SS_SAVING_PARAMETERS_NOT_SUPPORTED;
                return -EINVAL;
        }
        changeable_values = (pc == 1);
        all_pages = (page_code == 0x3f);

        /* Write the mode parameter header.  Fixed values are: default
         * medium type, no cache control (DPOFUA), and no block descriptors.
         * The only variable value is the WriteProtect bit.  We will fill in
         * the mode data length later. */
        memset(buf, 0, 8);
        if (mscmnd == SC_MODE_SENSE_6) {
                buf[2] = (curlun->ro ? 0x80 : 0x00);            /* WP, DPOFUA */
                buf += 4;
                limit = 255;
        } else {                        /* SC_MODE_SENSE_10 */
                buf[3] = (curlun->ro ? 0x80 : 0x00);            /* WP, DPOFUA */
                buf += 8;
                limit = 65535;          /* Should really be FSG_BUFLEN */
        }

        /* No block descriptors */

        /* The mode pages, in numerical order.  The only page we support
         * is the Caching page. */
        if (page_code == 0x08 || all_pages) {
                valid_page = 1;
                buf[0] = 0x08;          /* Page code */
                buf[1] = 10;            /* Page length */
                memset(buf+2, 0, 10);   /* None of the fields are changeable */

                if (!changeable_values) {
                        buf[2] = 0x04;  /* Write cache enable, */
                                        /* Read cache not disabled */
                                        /* No cache retention priorities */
                        put_unaligned_be16(0xffff, &buf[4]);
                                        /* Don't disable prefetch */
                                        /* Minimum prefetch = 0 */
                        put_unaligned_be16(0xffff, &buf[8]);
                                        /* Maximum prefetch */
                        put_unaligned_be16(0xffff, &buf[10]);
                                        /* Maximum prefetch ceiling */
                }
                buf += 12;
        }

        /* Check that a valid page was requested and the mode data length
         * isn't too long. */
        len = buf - buf0;
        if (!valid_page || len > limit) {
                curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                return -EINVAL;
        }

        /*  Store the mode data length */
        if (mscmnd == SC_MODE_SENSE_6)
                buf0[0] = len - 1;
        else
                put_unaligned_be16(len - 2, buf0);
        return len;
}


static int do_start_stop(struct fsg_common *common)
{
        struct fsg_lun  *curlun = &common->luns[common->lun];

        if (!curlun) {
                return -EINVAL;
        } else if (!curlun->removable) {
                curlun->sense_data = SS_INVALID_COMMAND;
                return -EINVAL;
        }

        return 0;
}

static int do_prevent_allow(struct fsg_common *common)
{
        struct fsg_lun  *curlun = &common->luns[common->lun];
        int             prevent;

        if (!curlun->removable) {
                curlun->sense_data = SS_INVALID_COMMAND;
                return -EINVAL;
        }

        prevent = common->cmnd[4] & 0x01;
        if ((common->cmnd[4] & ~0x01) != 0) {   /* Mask away Prevent */
                curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                return -EINVAL;
        }

        if (curlun->prevent_medium_removal && !prevent)
                fsg_lun_fsync_sub(curlun);
        curlun->prevent_medium_removal = prevent;
        return 0;
}


static int do_read_format_capacities(struct fsg_common *common,
                        struct fsg_buffhd *bh)
{
        struct fsg_lun  *curlun = &common->luns[common->lun];
        u8              *buf = (u8 *) bh->buf;

        buf[0] = buf[1] = buf[2] = 0;
        buf[3] = 8;     /* Only the Current/Maximum Capacity Descriptor */
        buf += 4;

        put_unaligned_be32(curlun->num_sectors, &buf[0]);
                                                /* Number of blocks */
        put_unaligned_be32(512, &buf[4]);       /* Block length */
        buf[4] = 0x02;                          /* Current capacity */
        return 12;
}


static int do_mode_select(struct fsg_common *common, struct fsg_buffhd *bh)
{
        struct fsg_lun  *curlun = &common->luns[common->lun];

        /* We don't support MODE SELECT */
        if (curlun)
                curlun->sense_data = SS_INVALID_COMMAND;
        return -EINVAL;
}


/*-------------------------------------------------------------------------*/

static int halt_bulk_in_endpoint(struct fsg_dev *fsg)
{
        int     rc;

        rc = fsg_set_halt(fsg, fsg->bulk_in);
        if (rc == -EAGAIN)
                VDBG(fsg, "delayed bulk-in endpoint halt\n");
        while (rc != 0) {
                if (rc != -EAGAIN) {
                        WARNING(fsg, "usb_ep_set_halt -> %d\n", rc);
                        rc = 0;
                        break;
                }

                rc = usb_ep_set_halt(fsg->bulk_in);
        }
        return rc;
}

static int wedge_bulk_in_endpoint(struct fsg_dev *fsg)
{
        int     rc;

        DBG(fsg, "bulk-in set wedge\n");
        rc = 0; /* usb_ep_set_wedge(fsg->bulk_in); */
        if (rc == -EAGAIN)
                VDBG(fsg, "delayed bulk-in endpoint wedge\n");
        while (rc != 0) {
                if (rc != -EAGAIN) {
                        WARNING(fsg, "usb_ep_set_wedge -> %d\n", rc);
                        rc = 0;
                        break;
                }
        }
        return rc;
}

static int pad_with_zeros(struct fsg_dev *fsg)
{
        struct fsg_buffhd       *bh = fsg->common->next_buffhd_to_fill;
        u32                     nkeep = bh->inreq->length;
        u32                     nsend;
        int                     rc;

        bh->state = BUF_STATE_EMPTY;            /* For the first iteration */
        fsg->common->usb_amount_left = nkeep + fsg->common->residue;
        while (fsg->common->usb_amount_left > 0) {

                /* Wait for the next buffer to be free */
                while (bh->state != BUF_STATE_EMPTY) {
                        rc = sleep_thread(fsg->common);
                        if (rc)
                                return rc;
                }

                nsend = min(fsg->common->usb_amount_left, FSG_BUFLEN);
                memset(bh->buf + nkeep, 0, nsend - nkeep);
                bh->inreq->length = nsend;
                bh->inreq->zero = 0;
                start_transfer(fsg, fsg->bulk_in, bh->inreq,
                                &bh->inreq_busy, &bh->state);
                bh = fsg->common->next_buffhd_to_fill = bh->next;
                fsg->common->usb_amount_left -= nsend;
                nkeep = 0;
        }
        return 0;
}

static int throw_away_data(struct fsg_common *common)
{
        struct fsg_buffhd       *bh;
        u32                     amount;
        int                     rc;

        for (bh = common->next_buffhd_to_drain;
             bh->state != BUF_STATE_EMPTY || common->usb_amount_left > 0;
             bh = common->next_buffhd_to_drain) {

                /* Throw away the data in a filled buffer */
                if (bh->state == BUF_STATE_FULL) {
                        bh->state = BUF_STATE_EMPTY;
                        common->next_buffhd_to_drain = bh->next;

                        /* A short packet or an error ends everything */
                        if (bh->outreq->actual != bh->outreq->length ||
                                        bh->outreq->status != 0) {
                                raise_exception(common,
                                                FSG_STATE_ABORT_BULK_OUT);
                                return -EINTR;
                        }
                        continue;
                }

                /* Try to submit another request if we need one */
                bh = common->next_buffhd_to_fill;
                if (bh->state == BUF_STATE_EMPTY
                 && common->usb_amount_left > 0) {
                        amount = min(common->usb_amount_left, FSG_BUFLEN);

                        /* amount is always divisible by 512, hence by
                         * the bulk-out maxpacket size */
                        bh->outreq->length = amount;
                        bh->bulk_out_intended_length = amount;
                        bh->outreq->short_not_ok = 1;
                        START_TRANSFER_OR(common, bulk_out, bh->outreq,
                                          &bh->outreq_busy, &bh->state)
                                /* Don't know what to do if
                                 * common->fsg is NULL */
                                return -EIO;
                        common->next_buffhd_to_fill = bh->next;
                        common->usb_amount_left -= amount;
                        continue;
                }

                /* Otherwise wait for something to happen */
                rc = sleep_thread(common);
                if (rc)
                        return rc;
        }
        return 0;
}


static int finish_reply(struct fsg_common *common)
{
        struct fsg_buffhd       *bh = common->next_buffhd_to_fill;
        int                     rc = 0;

        switch (common->data_dir) {
        case DATA_DIR_NONE:
                break;                  /* Nothing to send */

        /* If we don't know whether the host wants to read or write,
         * this must be CB or CBI with an unknown command.  We mustn't
         * try to send or receive any data.  So stall both bulk pipes
         * if we can and wait for a reset. */
        case DATA_DIR_UNKNOWN:
                if (!common->can_stall) {
                        /* Nothing */
                } else if (fsg_is_set(common)) {
                        fsg_set_halt(common->fsg, common->fsg->bulk_out);
                        rc = halt_bulk_in_endpoint(common->fsg);
                } else {
                        /* Don't know what to do if common->fsg is NULL */
                        rc = -EIO;
                }
                break;

        /* All but the last buffer of data must have already been sent */
        case DATA_DIR_TO_HOST:
                if (common->data_size == 0) {
                        /* Nothing to send */

                /* If there's no residue, simply send the last buffer */
                } else if (common->residue == 0) {
                        bh->inreq->zero = 0;
                        START_TRANSFER_OR(common, bulk_in, bh->inreq,
                                          &bh->inreq_busy, &bh->state)
                                return -EIO;
                        common->next_buffhd_to_fill = bh->next;

                /* For Bulk-only, if we're allowed to stall then send the
                 * short packet and halt the bulk-in endpoint.  If we can't
                 * stall, pad out the remaining data with 0's. */
                } else if (common->can_stall) {
                        bh->inreq->zero = 1;
                        START_TRANSFER_OR(common, bulk_in, bh->inreq,
                                          &bh->inreq_busy, &bh->state)
                                /* Don't know what to do if
                                 * common->fsg is NULL */
                                rc = -EIO;
                        common->next_buffhd_to_fill = bh->next;
                        if (common->fsg)
                                rc = halt_bulk_in_endpoint(common->fsg);
                } else if (fsg_is_set(common)) {
                        rc = pad_with_zeros(common->fsg);
                } else {
                        /* Don't know what to do if common->fsg is NULL */
                        rc = -EIO;
                }
                break;

        /* We have processed all we want from the data the host has sent.
         * There may still be outstanding bulk-out requests. */
        case DATA_DIR_FROM_HOST:
                if (common->residue == 0) {
                        /* Nothing to receive */

                /* Did the host stop sending unexpectedly early? */
                } else if (common->short_packet_received) {
                        raise_exception(common, FSG_STATE_ABORT_BULK_OUT);
                        rc = -EINTR;

                /* We haven't processed all the incoming data.  Even though
                 * we may be allowed to stall, doing so would cause a race.
                 * The controller may already have ACK'ed all the remaining
                 * bulk-out packets, in which case the host wouldn't see a
                 * STALL.  Not realizing the endpoint was halted, it wouldn't
                 * clear the halt -- leading to problems later on. */
#if 0
                } else if (common->can_stall) {
                        if (fsg_is_set(common))
                                fsg_set_halt(common->fsg,
                                             common->fsg->bulk_out);
                        raise_exception(common, FSG_STATE_ABORT_BULK_OUT);
                        rc = -EINTR;
#endif

                /* We can't stall.  Read in the excess data and throw it
                 * all away. */
                } else {
                        rc = throw_away_data(common);
                }
                break;
        }
        return rc;
}


static int send_status(struct fsg_common *common)
{
        struct fsg_lun          *curlun = &common->luns[common->lun];
        struct fsg_buffhd       *bh;
        struct bulk_cs_wrap     *csw;
        int                     rc;
        u8                      status = USB_STATUS_PASS;
        u32                     sd, sdinfo = 0;

        /* Wait for the next buffer to become available */
        bh = common->next_buffhd_to_fill;
        while (bh->state != BUF_STATE_EMPTY) {
                rc = sleep_thread(common);
                if (rc)
                        return rc;
        }

        if (curlun)
                sd = curlun->sense_data;
        else if (common->bad_lun_okay)
                sd = SS_NO_SENSE;
        else
                sd = SS_LOGICAL_UNIT_NOT_SUPPORTED;

        if (common->phase_error) {
                DBG(common, "sending phase-error status\n");
                status = USB_STATUS_PHASE_ERROR;
                sd = SS_INVALID_COMMAND;
        } else if (sd != SS_NO_SENSE) {
                DBG(common, "sending command-failure status\n");
                status = USB_STATUS_FAIL;
                VDBG(common, "  sense data: SK x%02x, ASC x%02x, ASCQ x%02x;"
                        "  info x%x\n",
                        SK(sd), ASC(sd), ASCQ(sd), sdinfo);
        }

        /* Store and send the Bulk-only CSW */
        csw = (void *)bh->buf;

        csw->Signature = cpu_to_le32(USB_BULK_CS_SIG);
        csw->Tag = common->tag;
        csw->Residue = cpu_to_le32(common->residue);
        csw->Status = status;

        bh->inreq->length = USB_BULK_CS_WRAP_LEN;
        bh->inreq->zero = 0;
        START_TRANSFER_OR(common, bulk_in, bh->inreq,
                          &bh->inreq_busy, &bh->state)
                /* Don't know what to do if common->fsg is NULL */
                return -EIO;

        common->next_buffhd_to_fill = bh->next;
        return 0;
}


/*-------------------------------------------------------------------------*/

/* Check whether the command is properly formed and whether its data size
 * and direction agree with the values we already have. */
static int check_command(struct fsg_common *common, int cmnd_size,
                enum data_direction data_dir, unsigned int mask,
                int needs_medium, const char *name)
{
        int                     i;
        int                     lun = common->cmnd[1] >> 5;
        static const char       dirletter[4] = {'u', 'o', 'i', 'n'};
        char                    hdlen[20];
        struct fsg_lun          *curlun;

        hdlen[0] = 0;
        if (common->data_dir != DATA_DIR_UNKNOWN)
                sprintf(hdlen, ", H%c=%u", dirletter[(int) common->data_dir],
                                common->data_size);
        VDBG(common, "SCSI command: %s;  Dc=%d, D%c=%u;  Hc=%d%s\n",
             name, cmnd_size, dirletter[(int) data_dir],
             common->data_size_from_cmnd, common->cmnd_size, hdlen);

        /* We can't reply at all until we know the correct data direction
         * and size. */
        if (common->data_size_from_cmnd == 0)
                data_dir = DATA_DIR_NONE;
        if (common->data_size < common->data_size_from_cmnd) {
                /* Host data size < Device data size is a phase error.
                 * Carry out the command, but only transfer as much as
                 * we are allowed. */
                common->data_size_from_cmnd = common->data_size;
                common->phase_error = 1;
        }
        common->residue = common->data_size;
        common->usb_amount_left = common->data_size;

        /* Conflicting data directions is a phase error */
        if (common->data_dir != data_dir
         && common->data_size_from_cmnd > 0) {
                common->phase_error = 1;
                return -EINVAL;
        }

        /* Verify the length of the command itself */
        if (cmnd_size != common->cmnd_size) {

                /* Special case workaround: There are plenty of buggy SCSI
                 * implementations. Many have issues with cbw->Length
                 * field passing a wrong command size. For those cases we
                 * always try to work around the problem by using the length
                 * sent by the host side provided it is at least as large
                 * as the correct command length.
                 * Examples of such cases would be MS-Windows, which issues
                 * REQUEST SENSE with cbw->Length == 12 where it should
                 * be 6, and xbox360 issuing INQUIRY, TEST UNIT READY and
                 * REQUEST SENSE with cbw->Length == 10 where it should
                 * be 6 as well.
                 */
                if (cmnd_size <= common->cmnd_size) {
                        DBG(common, "%s is buggy! Expected length %d "
                            "but we got %d\n", name,
                            cmnd_size, common->cmnd_size);
                        cmnd_size = common->cmnd_size;
                } else {
                        common->phase_error = 1;
                        return -EINVAL;
                }
        }

        /* Check that the LUN values are consistent */
        if (common->lun != lun)
                DBG(common, "using LUN %d from CBW, not LUN %d from CDB\n",
                    common->lun, lun);

        /* Check the LUN */
        if (common->lun < common->nluns) {
                curlun = &common->luns[common->lun];
                if (common->cmnd[0] != SC_REQUEST_SENSE) {
                        curlun->sense_data = SS_NO_SENSE;
                        curlun->info_valid = 0;
                }
        } else {
                curlun = NULL;
                common->bad_lun_okay = 0;

                /* INQUIRY and REQUEST SENSE commands are explicitly allowed
                 * to use unsupported LUNs; all others may not. */
                if (common->cmnd[0] != SC_INQUIRY &&
                    common->cmnd[0] != SC_REQUEST_SENSE) {
                        DBG(common, "unsupported LUN %d\n", common->lun);
                        return -EINVAL;
                }
        }
#if 0
        /* If a unit attention condition exists, only INQUIRY and
         * REQUEST SENSE commands are allowed; anything else must fail. */
        if (curlun && curlun->unit_attention_data != SS_NO_SENSE &&
                        common->cmnd[0] != SC_INQUIRY &&
                        common->cmnd[0] != SC_REQUEST_SENSE) {
                curlun->sense_data = curlun->unit_attention_data;
                curlun->unit_attention_data = SS_NO_SENSE;
                return -EINVAL;
        }
#endif
        /* Check that only command bytes listed in the mask are non-zero */
        common->cmnd[1] &= 0x1f;                        /* Mask away the LUN */
        for (i = 1; i < cmnd_size; ++i) {
                if (common->cmnd[i] && !(mask & (1 << i))) {
                        if (curlun)
                                curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                        return -EINVAL;
                }
        }

        return 0;
}


static int do_scsi_command(struct fsg_common *common)
{
        struct fsg_buffhd       *bh;
        int                     rc;
        int                     reply = -EINVAL;
        int                     i;
        static char             unknown[16];
        struct fsg_lun          *curlun = &common->luns[common->lun];

        dump_cdb(common);

        /* Wait for the next buffer to become available for data or status */
        bh = common->next_buffhd_to_fill;
        common->next_buffhd_to_drain = bh;
        while (bh->state != BUF_STATE_EMPTY) {
                rc = sleep_thread(common);
                if (rc)
                        return rc;
        }
        common->phase_error = 0;
        common->short_packet_received = 0;

        down_read(&common->filesem);    /* We're using the backing file */
        switch (common->cmnd[0]) {

        case SC_INQUIRY:
                common->data_size_from_cmnd = common->cmnd[4];
                reply = check_command(common, 6, DATA_DIR_TO_HOST,
                                      (1<<4), 0,
                                      "INQUIRY");
                if (reply == 0)
                        reply = do_inquiry(common, bh);
                break;

        case SC_MODE_SELECT_6:
                common->data_size_from_cmnd = common->cmnd[4];
                reply = check_command(common, 6, DATA_DIR_FROM_HOST,
                                      (1<<1) | (1<<4), 0,
                                      "MODE SELECT(6)");
                if (reply == 0)
                        reply = do_mode_select(common, bh);
                break;

        case SC_MODE_SELECT_10:
                common->data_size_from_cmnd =
                        get_unaligned_be16(&common->cmnd[7]);
                reply = check_command(common, 10, DATA_DIR_FROM_HOST,
                                      (1<<1) | (3<<7), 0,
                                      "MODE SELECT(10)");
                if (reply == 0)
                        reply = do_mode_select(common, bh);
                break;

        case SC_MODE_SENSE_6:
                common->data_size_from_cmnd = common->cmnd[4];
                reply = check_command(common, 6, DATA_DIR_TO_HOST,
                                      (1<<1) | (1<<2) | (1<<4), 0,
                                      "MODE SENSE(6)");
                if (reply == 0)
                        reply = do_mode_sense(common, bh);
                break;

        case SC_MODE_SENSE_10:
                common->data_size_from_cmnd =
                        get_unaligned_be16(&common->cmnd[7]);
                reply = check_command(common, 10, DATA_DIR_TO_HOST,
                                      (1<<1) | (1<<2) | (3<<7), 0,
                                      "MODE SENSE(10)");
                if (reply == 0)
                        reply = do_mode_sense(common, bh);
                break;

        case SC_PREVENT_ALLOW_MEDIUM_REMOVAL:
                common->data_size_from_cmnd = 0;
                reply = check_command(common, 6, DATA_DIR_NONE,
                                      (1<<4), 0,
                                      "PREVENT-ALLOW MEDIUM REMOVAL");
                if (reply == 0)
                        reply = do_prevent_allow(common);
                break;

        case SC_READ_6:
                i = common->cmnd[4];
                common->data_size_from_cmnd = (i == 0 ? 256 : i) << 9;
                reply = check_command(common, 6, DATA_DIR_TO_HOST,
                                      (7<<1) | (1<<4), 1,
                                      "READ(6)");
                if (reply == 0)
                        reply = do_read(common);
                break;

        case SC_READ_10:
                common->data_size_from_cmnd =
                                get_unaligned_be16(&common->cmnd[7]) << 9;
                reply = check_command(common, 10, DATA_DIR_TO_HOST,
                                      (1<<1) | (0xf<<2) | (3<<7), 1,
                                      "READ(10)");
                if (reply == 0)
                        reply = do_read(common);
                break;

        case SC_READ_12:
                common->data_size_from_cmnd =
                                get_unaligned_be32(&common->cmnd[6]) << 9;
                reply = check_command(common, 12, DATA_DIR_TO_HOST,
                                      (1<<1) | (0xf<<2) | (0xf<<6), 1,
                                      "READ(12)");
                if (reply == 0)
                        reply = do_read(common);
                break;

        case SC_READ_CAPACITY:
                common->data_size_from_cmnd = 8;
                reply = check_command(common, 10, DATA_DIR_TO_HOST,
                                      (0xf<<2) | (1<<8), 1,
                                      "READ CAPACITY");
                if (reply == 0)
                        reply = do_read_capacity(common, bh);
                break;

        case SC_READ_HEADER:
                if (!common->luns[common->lun].cdrom)
                        goto unknown_cmnd;
                common->data_size_from_cmnd =
                        get_unaligned_be16(&common->cmnd[7]);
                reply = check_command(common, 10, DATA_DIR_TO_HOST,
                                      (3<<7) | (0x1f<<1), 1,
                                      "READ HEADER");
                if (reply == 0)
                        reply = do_read_header(common, bh);
                break;

        case SC_READ_TOC:
                if (!common->luns[common->lun].cdrom)
                        goto unknown_cmnd;
                common->data_size_from_cmnd =
                        get_unaligned_be16(&common->cmnd[7]);
                reply = check_command(common, 10, DATA_DIR_TO_HOST,
                                      (7<<6) | (1<<1), 1,
                                      "READ TOC");
                if (reply == 0)
                        reply = do_read_toc(common, bh);
                break;

        case SC_READ_FORMAT_CAPACITIES:
                common->data_size_from_cmnd =
                        get_unaligned_be16(&common->cmnd[7]);
                reply = check_command(common, 10, DATA_DIR_TO_HOST,
                                      (3<<7), 1,
                                      "READ FORMAT CAPACITIES");
                if (reply == 0)
                        reply = do_read_format_capacities(common, bh);
                break;

        case SC_REQUEST_SENSE:
                common->data_size_from_cmnd = common->cmnd[4];
                reply = check_command(common, 6, DATA_DIR_TO_HOST,
                                      (1<<4), 0,
                                      "REQUEST SENSE");
                if (reply == 0)
                        reply = do_request_sense(common, bh);
                break;

        case SC_START_STOP_UNIT:
                common->data_size_from_cmnd = 0;
                reply = check_command(common, 6, DATA_DIR_NONE,
                                      (1<<1) | (1<<4), 0,
                                      "START-STOP UNIT");
                if (reply == 0)
                        reply = do_start_stop(common);
                break;

        case SC_SYNCHRONIZE_CACHE:
                common->data_size_from_cmnd = 0;
                reply = check_command(common, 10, DATA_DIR_NONE,
                                      (0xf<<2) | (3<<7), 1,
                                      "SYNCHRONIZE CACHE");
                if (reply == 0)
                        reply = do_synchronize_cache(common);
                break;

        case SC_TEST_UNIT_READY:
                common->data_size_from_cmnd = 0;
                reply = check_command(common, 6, DATA_DIR_NONE,
                                0, 1,
                                "TEST UNIT READY");
                break;

        /* Although optional, this command is used by MS-Windows.  We
         * support a minimal version: BytChk must be 0. */
        case SC_VERIFY:
                common->data_size_from_cmnd = 0;
                reply = check_command(common, 10, DATA_DIR_NONE,
                                      (1<<1) | (0xf<<2) | (3<<7), 1,
                                      "VERIFY");
                if (reply == 0)
                        reply = do_verify(common);
                break;

        case SC_WRITE_6:
                i = common->cmnd[4];
                common->data_size_from_cmnd = (i == 0 ? 256 : i) << 9;
                reply = check_command(common, 6, DATA_DIR_FROM_HOST,
                                      (7<<1) | (1<<4), 1,
                                      "WRITE(6)");
                if (reply == 0)
                        reply = do_write(common);
                break;

        case SC_WRITE_10:
                common->data_size_from_cmnd =
                                get_unaligned_be16(&common->cmnd[7]) << 9;
                reply = check_command(common, 10, DATA_DIR_FROM_HOST,
                                      (1<<1) | (0xf<<2) | (3<<7), 1,
                                      "WRITE(10)");
                if (reply == 0)
                        reply = do_write(common);
                break;

        case SC_WRITE_12:
                common->data_size_from_cmnd =
                                get_unaligned_be32(&common->cmnd[6]) << 9;
                reply = check_command(common, 12, DATA_DIR_FROM_HOST,

                                      (1<<1) | (0xf<<2) | (0xf<<6), 1,
                                      "WRITE(12)");
                if (reply == 0)
                        reply = do_write(common);
                break;

        /* Some mandatory commands that we recognize but don't implement.
         * They don't mean much in this setting.  It's left as an exercise
         * for anyone interested to implement RESERVE and RELEASE in terms
         * of Posix locks. */
        case SC_FORMAT_UNIT:
        case SC_RELEASE:
        case SC_RESERVE:
        case SC_SEND_DIAGNOSTIC:
                /* Fall through */

        default:
unknown_cmnd:
                common->data_size_from_cmnd = 0;
                sprintf(unknown, "Unknown x%02x", common->cmnd[0]);
                reply = check_command(common, common->cmnd_size,
                                      DATA_DIR_UNKNOWN, 0xff, 0, unknown);
                if (reply == 0) {
                        curlun->sense_data = SS_INVALID_COMMAND;
                        reply = -EINVAL;
                }
                break;
        }
        up_read(&common->filesem);

        if (reply == -EINTR)
                return -EINTR;

        /* Set up the single reply buffer for finish_reply() */
        if (reply == -EINVAL)
                reply = 0;              /* Error reply length */
        if (reply >= 0 && common->data_dir == DATA_DIR_TO_HOST) {
                reply = min((u32) reply, common->data_size_from_cmnd);
                bh->inreq->length = reply;
                bh->state = BUF_STATE_FULL;
                common->residue -= reply;
        }                               /* Otherwise it's already set */

        return 0;
}

/*-------------------------------------------------------------------------*/

static int received_cbw(struct fsg_dev *fsg, struct fsg_buffhd *bh)
{
        struct usb_request      *req = bh->outreq;
        struct fsg_bulk_cb_wrap *cbw = req->buf;
        struct fsg_common       *common = fsg->common;

        /* Was this a real packet?  Should it be ignored? */
        if (req->status || test_bit(IGNORE_BULK_OUT, &fsg->atomic_bitflags))
                return -EINVAL;

        /* Is the CBW valid? */
        if (req->actual != USB_BULK_CB_WRAP_LEN ||
                        cbw->Signature != cpu_to_le32(
                                USB_BULK_CB_SIG)) {
                DBG(fsg, "invalid CBW: len %u sig 0x%x\n",
                                req->actual,
                                le32_to_cpu(cbw->Signature));

                /* The Bulk-only spec says we MUST stall the IN endpoint
                 * (6.6.1), so it's unavoidable.  It also says we must
                 * retain this state until the next reset, but there's
                 * no way to tell the controller driver it should ignore
                 * Clear-Feature(HALT) requests.
                 *
                 * We aren't required to halt the OUT endpoint; instead
                 * we can simply accept and discard any data received
                 * until the next reset. */
                wedge_bulk_in_endpoint(fsg);
                generic_set_bit(IGNORE_BULK_OUT, &fsg->atomic_bitflags);
                return -EINVAL;
        }

        /* Is the CBW meaningful? */
        if (cbw->Lun >= FSG_MAX_LUNS || cbw->Flags & ~USB_BULK_IN_FLAG ||
                        cbw->Length <= 0 || cbw->Length > MAX_COMMAND_SIZE) {
                DBG(fsg, "non-meaningful CBW: lun = %u, flags = 0x%x, "
                                "cmdlen %u\n",
                                cbw->Lun, cbw->Flags, cbw->Length);

                /* We can do anything we want here, so let's stall the
                 * bulk pipes if we are allowed to. */
                if (common->can_stall) {
                        fsg_set_halt(fsg, fsg->bulk_out);
                        halt_bulk_in_endpoint(fsg);
                }
                return -EINVAL;
        }

        /* Save the command for later */
        common->cmnd_size = cbw->Length;
        memcpy(common->cmnd, cbw->CDB, common->cmnd_size);
        if (cbw->Flags & USB_BULK_IN_FLAG)
                common->data_dir = DATA_DIR_TO_HOST;
        else
                common->data_dir = DATA_DIR_FROM_HOST;
        common->data_size = le32_to_cpu(cbw->DataTransferLength);
        if (common->data_size == 0)
                common->data_dir = DATA_DIR_NONE;
        common->lun = cbw->Lun;
        common->tag = cbw->Tag;
        return 0;
}


static int get_next_command(struct fsg_common *common)
{
        struct fsg_buffhd       *bh;
        int                     rc = 0;

        /* Wait for the next buffer to become available */
        bh = common->next_buffhd_to_fill;
        while (bh->state != BUF_STATE_EMPTY) {
                rc = sleep_thread(common);
                if (rc)
                        return rc;
        }

        /* Queue a request to read a Bulk-only CBW */
        set_bulk_out_req_length(common, bh, USB_BULK_CB_WRAP_LEN);
        bh->outreq->short_not_ok = 1;
        START_TRANSFER_OR(common, bulk_out, bh->outreq,
                          &bh->outreq_busy, &bh->state)
                /* Don't know what to do if common->fsg is NULL */
                return -EIO;

        /* We will drain the buffer in software, which means we
         * can reuse it for the next filling.  No need to advance
         * next_buffhd_to_fill. */

        /* Wait for the CBW to arrive */
        while (bh->state != BUF_STATE_FULL) {
                rc = sleep_thread(common);
                if (rc)
                        return rc;
        }

        rc = fsg_is_set(common) ? received_cbw(common->fsg, bh) : -EIO;
        bh->state = BUF_STATE_EMPTY;

        return rc;
}


/*-------------------------------------------------------------------------*/

static int enable_endpoint(struct fsg_common *common, struct usb_ep *ep,
                const struct usb_endpoint_descriptor *d)
{
        int     rc;

        ep->driver_data = common;
        rc = usb_ep_enable(ep, d);
        if (rc)
                ERROR(common, "can't enable %s, result %d\n", ep->name, rc);
        return rc;
}

static int alloc_request(struct fsg_common *common, struct usb_ep *ep,
                struct usb_request **preq)
{
        *preq = usb_ep_alloc_request(ep, GFP_ATOMIC);
        if (*preq)
                return 0;
        ERROR(common, "can't allocate request for %s\n", ep->name);
        return -ENOMEM;
}

/* Reset interface setting and re-init endpoint state (toggle etc). */
static int do_set_interface(struct fsg_common *common, struct fsg_dev *new_fsg)
{
        const struct usb_endpoint_descriptor *d;
        struct fsg_dev *fsg;
        int i, rc = 0;

        if (common->running)
                DBG(common, "reset interface\n");

reset:
        /* Deallocate the requests */
        if (common->fsg) {
                fsg = common->fsg;

                for (i = 0; i < FSG_NUM_BUFFERS; ++i) {
                        struct fsg_buffhd *bh = &common->buffhds[i];

                        if (bh->inreq) {
                                usb_ep_free_request(fsg->bulk_in, bh->inreq);
                                bh->inreq = NULL;
                        }
                        if (bh->outreq) {
                                usb_ep_free_request(fsg->bulk_out, bh->outreq);
                                bh->outreq = NULL;
                        }
                }

                /* Disable the endpoints */
                if (fsg->bulk_in_enabled) {
                        usb_ep_disable(fsg->bulk_in);
                        fsg->bulk_in_enabled = 0;
                }
                if (fsg->bulk_out_enabled) {
                        usb_ep_disable(fsg->bulk_out);
                        fsg->bulk_out_enabled = 0;
                }

                common->fsg = NULL;
                /* wake_up(&common->fsg_wait); */
        }

        common->running = 0;
        if (!new_fsg || rc)
                return rc;

        common->fsg = new_fsg;
        fsg = common->fsg;

        /* Enable the endpoints */
        d = fsg_ep_desc(common->gadget,
                        &fsg_fs_bulk_in_desc, &fsg_hs_bulk_in_desc);
        rc = enable_endpoint(common, fsg->bulk_in, d);
        if (rc)
                goto reset;
        fsg->bulk_in_enabled = 1;

        d = fsg_ep_desc(common->gadget,
                        &fsg_fs_bulk_out_desc, &fsg_hs_bulk_out_desc);
        rc = enable_endpoint(common, fsg->bulk_out, d);
        if (rc)
                goto reset;
        fsg->bulk_out_enabled = 1;
        common->bulk_out_maxpacket =
                                le16_to_cpu(get_unaligned(&d->wMaxPacketSize));
        generic_clear_bit(IGNORE_BULK_OUT, &fsg->atomic_bitflags);

        /* Allocate the requests */
        for (i = 0; i < FSG_NUM_BUFFERS; ++i) {
                struct fsg_buffhd       *bh = &common->buffhds[i];

                rc = alloc_request(common, fsg->bulk_in, &bh->inreq);
                if (rc)
                        goto reset;
                rc = alloc_request(common, fsg->bulk_out, &bh->outreq);
                if (rc)
                        goto reset;
                bh->inreq->buf = bh->outreq->buf = bh->buf;
                bh->inreq->context = bh->outreq->context = bh;
                bh->inreq->complete = bulk_in_complete;
                bh->outreq->complete = bulk_out_complete;
        }

        common->running = 1;

        return rc;
}


/****************************** ALT CONFIGS ******************************/


static int fsg_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
{
        struct fsg_dev *fsg = fsg_from_func(f);
        fsg->common->new_fsg = fsg;
        raise_exception(fsg->common, FSG_STATE_CONFIG_CHANGE);
        return 0;
}

static void fsg_disable(struct usb_function *f)
{
        struct fsg_dev *fsg = fsg_from_func(f);
        fsg->common->new_fsg = NULL;
        raise_exception(fsg->common, FSG_STATE_CONFIG_CHANGE);
}

/*-------------------------------------------------------------------------*/

static void handle_exception(struct fsg_common *common)
{
        int                     i;
        struct fsg_buffhd       *bh;
        enum fsg_state          old_state;
        struct fsg_lun          *curlun;
        unsigned int            exception_req_tag;

        /* Cancel all the pending transfers */
        if (common->fsg) {
                for (i = 0; i < FSG_NUM_BUFFERS; ++i) {
                        bh = &common->buffhds[i];
                        if (bh->inreq_busy)
                                usb_ep_dequeue(common->fsg->bulk_in, bh->inreq);
                        if (bh->outreq_busy)
                                usb_ep_dequeue(common->fsg->bulk_out,
                                               bh->outreq);
                }

                /* Wait until everything is idle */
                for (;;) {
                        int num_active = 0;
                        for (i = 0; i < FSG_NUM_BUFFERS; ++i) {
                                bh = &common->buffhds[i];
                                num_active += bh->inreq_busy + bh->outreq_busy;
                        }
                        if (num_active == 0)
                                break;
                        if (sleep_thread(common))
                                return;
                }

                /* Clear out the controller's fifos */
                if (common->fsg->bulk_in_enabled)
                        usb_ep_fifo_flush(common->fsg->bulk_in);
                if (common->fsg->bulk_out_enabled)
                        usb_ep_fifo_flush(common->fsg->bulk_out);
        }

        /* Reset the I/O buffer states and pointers, the SCSI
         * state, and the exception.  Then invoke the handler. */

        for (i = 0; i < FSG_NUM_BUFFERS; ++i) {
                bh = &common->buffhds[i];
                bh->state = BUF_STATE_EMPTY;
        }
        common->next_buffhd_to_fill = &common->buffhds[0];
        common->next_buffhd_to_drain = &common->buffhds[0];
        exception_req_tag = common->exception_req_tag;
        old_state = common->state;

        if (old_state == FSG_STATE_ABORT_BULK_OUT)
                common->state = FSG_STATE_STATUS_PHASE;
        else {
                for (i = 0; i < common->nluns; ++i) {
                        curlun = &common->luns[i];
                        curlun->sense_data = SS_NO_SENSE;
                        curlun->info_valid = 0;
                }
                common->state = FSG_STATE_IDLE;
        }

        /* Carry out any extra actions required for the exception */
        switch (old_state) {
        case FSG_STATE_ABORT_BULK_OUT:
                send_status(common);

                if (common->state == FSG_STATE_STATUS_PHASE)
                        common->state = FSG_STATE_IDLE;
                break;

        case FSG_STATE_RESET:
                /* In case we were forced against our will to halt a
                 * bulk endpoint, clear the halt now.  (The SuperH UDC
                 * requires this.) */
                if (!fsg_is_set(common))
                        break;
                if (test_and_clear_bit(IGNORE_BULK_OUT,
                                       &common->fsg->atomic_bitflags))
                        usb_ep_clear_halt(common->fsg->bulk_in);

                if (common->ep0_req_tag == exception_req_tag)
                        ep0_queue(common);      /* Complete the status stage */

                break;

        case FSG_STATE_CONFIG_CHANGE:
                do_set_interface(common, common->new_fsg);
                break;

        case FSG_STATE_EXIT:
        case FSG_STATE_TERMINATED:
                do_set_interface(common, NULL);         /* Free resources */
                common->state = FSG_STATE_TERMINATED;   /* Stop the thread */
                break;

        case FSG_STATE_INTERFACE_CHANGE:
        case FSG_STATE_DISCONNECT:
        case FSG_STATE_COMMAND_PHASE:
        case FSG_STATE_DATA_PHASE:
        case FSG_STATE_STATUS_PHASE:
        case FSG_STATE_IDLE:
                break;
        }
}

/*-------------------------------------------------------------------------*/

int fsg_main_thread(void *common_)
{
        int ret;
        struct fsg_common       *common = the_fsg_common;
        /* The main loop */
        do {
                if (exception_in_progress(common)) {
                        handle_exception(common);
                        continue;
                }

                if (!common->running) {
                        ret = sleep_thread(common);
                        if (ret)
                                return ret;

                        continue;
                }

                ret = get_next_command(common);
                if (ret)
                        return ret;

                if (!exception_in_progress(common))
                        common->state = FSG_STATE_DATA_PHASE;

                if (do_scsi_command(common) || finish_reply(common))
                        continue;

                if (!exception_in_progress(common))
                        common->state = FSG_STATE_STATUS_PHASE;

                if (send_status(common))
                        continue;

                if (!exception_in_progress(common))
                        common->state = FSG_STATE_IDLE;
        } while (0);

        common->thread_task = NULL;

        return 0;
}

static void fsg_common_release(struct kref *ref);

static struct fsg_common *fsg_common_init(struct fsg_common *common,
                                          struct usb_composite_dev *cdev)
{
        struct usb_gadget *gadget = cdev->gadget;
        struct fsg_buffhd *bh;
        struct fsg_lun *curlun;
        int nluns, i, rc;

        /* Find out how many LUNs there should be */
        nluns = ums_count;
        if (nluns < 1 || nluns > FSG_MAX_LUNS) {
                printf("invalid number of LUNs: %u\n", nluns);
                return ERR_PTR(-EINVAL);
        }

        /* Allocate? */
        if (!common) {
                common = calloc(sizeof(*common), 1);
                if (!common)
                        return ERR_PTR(-ENOMEM);
                common->free_storage_on_release = 1;
        } else {
                memset(common, 0, sizeof(*common));
                common->free_storage_on_release = 0;
        }

        common->ops = NULL;
        common->private_data = NULL;

        common->gadget = gadget;
        common->ep0 = gadget->ep0;
        common->ep0req = cdev->req;

        /* Maybe allocate device-global string IDs, and patch descriptors */
        if (fsg_strings[FSG_STRING_INTERFACE].id == 0) {
                rc = usb_string_id(cdev);
                if (unlikely(rc < 0))
                        goto error_release;
                fsg_strings[FSG_STRING_INTERFACE].id = rc;
                fsg_intf_desc.iInterface = rc;
        }

        /* Create the LUNs, open their backing files, and register the
         * LUN devices in sysfs. */
        curlun = calloc(nluns, sizeof *curlun);
        if (!curlun) {
                rc = -ENOMEM;
                goto error_release;
        }
        common->nluns = nluns;

        for (i = 0; i < nluns; i++) {
                common->luns[i].removable = 1;

                rc = fsg_lun_open(&common->luns[i], ums[i].num_sectors, "");
                if (rc)
                        goto error_luns;
        }
        common->lun = 0;

        /* Data buffers cyclic list */
        bh = common->buffhds;

        i = FSG_NUM_BUFFERS;
        goto buffhds_first_it;
        do {
                bh->next = bh + 1;
                ++bh;
buffhds_first_it:
                bh->inreq_busy = 0;
                bh->outreq_busy = 0;
                bh->buf = memalign(CONFIG_SYS_CACHELINE_SIZE, FSG_BUFLEN);
                if (unlikely(!bh->buf)) {
                        rc = -ENOMEM;
                        goto error_release;
                }
        } while (--i);
        bh->next = common->buffhds;

        snprintf(common->inquiry_string, sizeof common->inquiry_string,
                 "%-8s%-16s%04x",
                 "Linux   ",
                 "File-Store Gadget",
                 0xffff);

        /* Some peripheral controllers are known not to be able to
         * halt bulk endpoints correctly.  If one of them is present,
         * disable stalls.
         */

        /* Tell the thread to start working */
        common->thread_task =
                kthread_create(fsg_main_thread, common,
                               OR(cfg->thread_name, "file-storage"));
        if (IS_ERR(common->thread_task)) {
                rc = PTR_ERR(common->thread_task);
                goto error_release;
        }

#undef OR
        /* Information */
        INFO(common, FSG_DRIVER_DESC ", version: " FSG_DRIVER_VERSION "\n");
        INFO(common, "Number of LUNs=%d\n", common->nluns);

        return common;

error_luns:
        common->nluns = i + 1;
error_release:
        common->state = FSG_STATE_TERMINATED;   /* The thread is dead */
        /* Call fsg_common_release() directly, ref might be not
         * initialised */
        fsg_common_release(&common->ref);
        return ERR_PTR(rc);
}

static void fsg_common_release(struct kref *ref)
{
        struct fsg_common *common = container_of(ref, struct fsg_common, ref);

        /* If the thread isn't already dead, tell it to exit now */
        if (common->state != FSG_STATE_TERMINATED) {
                raise_exception(common, FSG_STATE_EXIT);
                wait_for_completion(&common->thread_notifier);
        }

        if (likely(common->luns)) {
                struct fsg_lun *lun = common->luns;
                unsigned i = common->nluns;

                /* In error recovery common->nluns may be zero. */
                for (; i; --i, ++lun)
                        fsg_lun_close(lun);

                kfree(common->luns);
        }

        {
                struct fsg_buffhd *bh = common->buffhds;
                unsigned i = FSG_NUM_BUFFERS;
                do {
                        kfree(bh->buf);
                } while (++bh, --i);
        }

        if (common->free_storage_on_release)
                kfree(common);
}


/*-------------------------------------------------------------------------*/

/**
 * usb_copy_descriptors - copy a vector of USB descriptors
 * @src: null-terminated vector to copy
 * Context: initialization code, which may sleep
 *
 * This makes a copy of a vector of USB descriptors.  Its primary use
 * is to support usb_function objects which can have multiple copies,
 * each needing different descriptors.  Functions may have static
 * tables of descriptors, which are used as templates and customized
 * with identifiers (for interfaces, strings, endpoints, and more)
 * as needed by a given function instance.
 */
struct usb_descriptor_header **
usb_copy_descriptors(struct usb_descriptor_header **src)
{
        struct usb_descriptor_header **tmp;
        unsigned bytes;
        unsigned n_desc;
        void *mem;
        struct usb_descriptor_header **ret;

        /* count descriptors and their sizes; then add vector size */
        for (bytes = 0, n_desc = 0, tmp = src; *tmp; tmp++, n_desc++)
                bytes += (*tmp)->bLength;
        bytes += (n_desc + 1) * sizeof(*tmp);

        mem = memalign(CONFIG_SYS_CACHELINE_SIZE, bytes);
        if (!mem)
                return NULL;

        /* fill in pointers starting at "tmp",
         * to descriptors copied starting at "mem";
         * and return "ret"
         */
        tmp = mem;
        ret = mem;
        mem += (n_desc + 1) * sizeof(*tmp);
        while (*src) {
                memcpy(mem, *src, (*src)->bLength);
                *tmp = mem;
                tmp++;
                mem += (*src)->bLength;
                src++;
        }
        *tmp = NULL;

        return ret;
}

static void fsg_unbind(struct usb_configuration *c, struct usb_function *f)
{
        struct fsg_dev          *fsg = fsg_from_func(f);

        DBG(fsg, "unbind\n");
        if (fsg->common->fsg == fsg) {
                fsg->common->new_fsg = NULL;
                raise_exception(fsg->common, FSG_STATE_CONFIG_CHANGE);
        }

        free(fsg->function.descriptors);
        free(fsg->function.hs_descriptors);
        kfree(fsg);
}

static int fsg_bind(struct usb_configuration *c, struct usb_function *f)
{
        struct fsg_dev          *fsg = fsg_from_func(f);
        struct usb_gadget       *gadget = c->cdev->gadget;
        int                     i;
        struct usb_ep           *ep;
        fsg->gadget = gadget;

        /* New interface */
        i = usb_interface_id(c, f);
        if (i < 0)
                return i;
        fsg_intf_desc.bInterfaceNumber = i;
        fsg->interface_number = i;

        /* Find all the endpoints we will use */
        ep = usb_ep_autoconfig(gadget, &fsg_fs_bulk_in_desc);
        if (!ep)
                goto autoconf_fail;
        ep->driver_data = fsg->common;  /* claim the endpoint */
        fsg->bulk_in = ep;

        ep = usb_ep_autoconfig(gadget, &fsg_fs_bulk_out_desc);
        if (!ep)
                goto autoconf_fail;
        ep->driver_data = fsg->common;  /* claim the endpoint */
        fsg->bulk_out = ep;

        /* Copy descriptors */
        f->descriptors = usb_copy_descriptors(fsg_fs_function);
        if (unlikely(!f->descriptors))
                return -ENOMEM;

        if (gadget_is_dualspeed(gadget)) {
                /* Assume endpoint addresses are the same for both speeds */
                fsg_hs_bulk_in_desc.bEndpointAddress =
                        fsg_fs_bulk_in_desc.bEndpointAddress;
                fsg_hs_bulk_out_desc.bEndpointAddress =
                        fsg_fs_bulk_out_desc.bEndpointAddress;
                f->hs_descriptors = usb_copy_descriptors(fsg_hs_function);
                if (unlikely(!f->hs_descriptors)) {
                        free(f->descriptors);
                        return -ENOMEM;
                }
        }
        return 0;

autoconf_fail:
        ERROR(fsg, "unable to autoconfigure all endpoints\n");
        return -ENOTSUPP;
}


/****************************** ADD FUNCTION ******************************/

static struct usb_gadget_strings *fsg_strings_array[] = {
        &fsg_stringtab,
        NULL,
};

static int fsg_bind_config(struct usb_composite_dev *cdev,
                           struct usb_configuration *c,
                           struct fsg_common *common)
{
        struct fsg_dev *fsg;
        int rc;

        fsg = calloc(1, sizeof *fsg);
        if (!fsg)
                return -ENOMEM;
        fsg->function.name        = FSG_DRIVER_DESC;
        fsg->function.strings     = fsg_strings_array;
        fsg->function.bind        = fsg_bind;
        fsg->function.unbind      = fsg_unbind;
        fsg->function.setup       = fsg_setup;
        fsg->function.set_alt     = fsg_set_alt;
        fsg->function.disable     = fsg_disable;

        fsg->common               = common;
        common->fsg               = fsg;
        /* Our caller holds a reference to common structure so we
         * don't have to be worry about it being freed until we return
         * from this function.  So instead of incrementing counter now
         * and decrement in error recovery we increment it only when
         * call to usb_add_function() was successful. */

        rc = usb_add_function(c, &fsg->function);

        if (rc)
                kfree(fsg);

        return rc;
}

int fsg_add(struct usb_configuration *c)
{
        struct fsg_common *fsg_common;

        fsg_common = fsg_common_init(NULL, c->cdev);

        fsg_common->vendor_name = 0;
        fsg_common->product_name = 0;
        fsg_common->release = 0xffff;

        fsg_common->ops = NULL;
        fsg_common->private_data = NULL;

        the_fsg_common = fsg_common;

        return fsg_bind_config(c->cdev, c, fsg_common);
}

int fsg_init(struct ums *ums_devs, int count, unsigned int controller_idx)
{
        ums = ums_devs;
        ums_count = count;
        controller_index = controller_idx;

        return 0;
}

DECLARE_GADGET_BIND_CALLBACK(usb_dnl_ums, fsg_add);